Browsing by Subject "Chemistry, Organic"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Open Access
    Intra- and intermolecular reactivity of organic diacyl systems
    (1988) Symes, Jillian Ellis; Modro, Tomasz A
    The mechanism or a thermal amino group transfer-fragmentation reaction yielding carboxyamides from mixed phosphoric-carboxylic anhydrides (RO(R¹R²N)P(O)OC(O)R³; R = R¹ = alkyl; R² = H, alkyl, aryl; R³ = alkyl, aryl) was elucidated from structure reactivity studies using a model system, R = R¹ = R² = Me, R³ = Ph. Kinetic data was obtained using ¹H nmr spectroscopy; MNDO molecular orbital and molecular mechanics calculations, and the crystal structure or N-methyl-2-benzoyloxy-2-oxo-1, 3, 2-oxazaphosphorinane (Pna2₁; a = 22.229(6)Å, b = 7.597(2)Å, c = 7.210(2)Å; v = 1217.6(6)ų. Final R = 3. 08% for 1037 reflections with I (rel )> 2αI (rel) and 15 7 parameters) were userul in providing additional in formation about the reaction mechanism .
  • Thumbnail Image
    Item
    Open Access
    Some non-cellulosic b-D-Glycans from plant sources
    (1987) Mabusela, Wilfred Thozamile; Stephen, A M
    The structures of some non-cellulosic β D-Glycans from three plant sources have been investigated and each was found to be characterised by linked D-pyranosyl a main chain consisting of β -(1-44)- sugars. The polysaccharides were, however, different in structural features in a manner apparently related to their respective locations within the organs of the plants concerned. The polysaccharides were isolated and purified using standard fractionation methods including chromatographic techniques and selective precipitation methods. Structural information was obtained by employing techniques such as methylation analysis (involving use of gas liquid chromatography mass spectrometry), optical rotation measurements, mass spectrometry and n.m.r. spectroscopy on the original polysaccharides and on degraded products obtained by methods such as acid- or enzyme-catalysed hydrolysis and Smith degradation.
  • Thumbnail Image
    Item
    Open Access
    Steroidal saponins and sapogenins from Agapanthus praecox Willd
    (1970) Mathew, George Ernest Albert; Stephen, A M
    Agapanthin, C₅₁H₈₄O₂₄, a steroidal saponin, isolated from rhizomes of Agapanthus praecox Willd., yielded, on acid hydrolysis, the steroidal sapogenin agspanthagenin and galactose and rhamnose in the molecular ratio of 3:l. The structure assigned to agapanthagenin has been confirmed oh the basis of further synthetic and spectroscopic evidence. The structure of a closely associated steroidal sapogenin, praecoxigenin, C₂₇H₄₀O₄ , has been partially elucidated.